Multiple Choice
Which of the following is NOT a molecular compound?
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Molecular Formula
Multiple Choice
Glyceraldehyde (M = 90.078 g/mol), a simple monosaccharide, is comprised of 39.999% C, 6.714% H, and 53.297% oxygen by atomic weight. What would be its molecular formula?
A
C3H6O3
B
CH2O
C
C3HO3
D
C2H8O2
Verified step by step guidance1
Step 1: Begin by understanding the problem. We need to determine the molecular formula of glyceraldehyde using its percentage composition by weight and its molar mass.
Step 2: Convert the percentage composition into grams assuming a 100 g sample. This means we have 39.999 g of carbon (C), 6.714 g of hydrogen (H), and 53.297 g of oxygen (O).
Step 3: Calculate the number of moles of each element in the sample using their atomic masses. Use the formula: \( \text{moles} = \frac{\text{mass}}{\text{atomic mass}} \). For carbon, \( \text{atomic mass} = 12.01 \text{ g/mol} \), for hydrogen, \( \text{atomic mass} = 1.008 \text{ g/mol} \), and for oxygen, \( \text{atomic mass} = 16.00 \text{ g/mol} \).
Step 4: Determine the simplest mole ratio of the elements by dividing the number of moles of each element by the smallest number of moles calculated in Step 3. This will give you the empirical formula.
Step 5: Use the molar mass of glyceraldehyde (90.078 g/mol) to convert the empirical formula to the molecular formula. Compare the molar mass of the empirical formula to the given molar mass to find the correct molecular formula.
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